iBreadBoard | Electronics mini Projcts | Circuit Borad Designs

With all the cool things that you can do with LEDs today, there is still one thing that’s lacking: simplicity. If you want to run a bunch of LEDs at a time, you usually end up spending a fair bit of time worrying about series and parallel combinations, matching brightness, and picking load resistors. Or, if you’re a beginner, maybe you only get one third of the way through the previous sentence– wondering if you’re already in over your head.

Suppose that you want to make a big LED display for your window or wall: maybe it’s your logo, a symbol, your favorite 8-bit character, or maybe even a sign that spells out words like “OPEN” or “ON AIR.” How do you go about it? The usual DIY solution involves drilling holes in a panel to fit your LEDs, then spending a heck of a lot of time wiring everything up– ending up with one resistor per LED (and a three-dimensional mess if you happen to look at the back side of the panel). And, if you do everything in the most obvious ways, it can even end up consuming a surprising amount of power.

While I have certainly spent my share of time constructing things with the aforementioned technique, at some point it becomes clear that there has to be a better way. In this day and age, shouldn’t LEDs be about as difficult to play with as, say, a Lite Bright? Today we are releasing a new open-source hardware and software design that takes some of the sting, complexity, and mess out of playing with LEDs. It’s a versatile and powerful light-emitting pegboard that lets you efficiently drive hundreds of LEDs in whatever configuration you like, without so much as calculating a single load resistor.

So how does it work?

The design is based on a large custom printed circuit board that provides a 25 x 25 grid of locations for LEDs; 625 in all. Around the edges of this array go resistors and transistors that serve to control the array, driven by a large AVR microcontroller. Once those peripheral components around the edges have been added, every one of the 625 LED locations is active, and an LED placed there will light up and be efficiently driven.

Circuit theory

The basic idea is that we have constructed a multiplexed array where only one row of the display is actually turned on at any given time. However, the microcontroller scans through the different rows so quickly that they all appear to be on continuously. The anodes of the LEDs in each column are connected together, and through a single resistor to the positive voltage rail, 4.5 V. Since only one row is ever on at a given time, that column resistor limits the amount of current through just one LED– effectively providing one load resistor for every LED that is on at a given time. The cathodes of the LEDs in each row are connected together and are controlled through a single NPN transistor driven by the microcontroller. This design inherently does not care which LED locations are populated and which are empty– performance is not affected by the number of LEDs in a given row.

Microcontroller

While there are some other ways that the circuit could be driven, we chose to use an ATmega164P microcontroller to drive the display. It is a relatively inexpensive AVR family microcontroller with 16 K of flash, hardly any of which is required for the basic row-scanning functions that we use. The most important thing is that it comes in a 40-pin package that can easily drive the 25 pins of the display and still have room left over for several extra I/O pins including analog to digital converters. One of the main reasons to pick a controller like that is that one of our design goals was for the whole circuit to be seriously hackable. What exactly can be done with that processor and its extra inputs is wide open. As a simple example, our default firmware uses a light sensor and can (optionally) turn off the display during the daytime.What does it look like?

First of all it should be stressed that the circuit board is huge: 12 x 15″. That’s because we’ve left enough room at each LED location to fit a “10 mm” LED. The pegboard area itself covers nearly a square foot of space. Immediately below the LED field is room for a battery box (3 x D-cell). On the lower left is the microcontroller and on the lower right there is a place for a power jack and a switch to select whether the board is powered from an adapter or from batteries.

Of course, what we really care about is what it looks like when there are things on the circuit board:

In the examples above, you can see our Evil Mad Scientist “Resist” logo, along with our electronic and sarcastic valentine’s day card. There are also closeups on 10 mm pink, green, and blue diffused LEDs, as well as 5 mm white clear LEDs installed in the panels.

How do you make it?

This project is fully documented, wide open, open source, and you can approach it from any direction you want. Start with the schematics and firmware, or start with a circuit board and a soldering iron. It’s all yours:

This is an easy way to drive a lot of LEDs– up to 625– in a big matrix. You can make an LED sign for your window, a geeky valentine for your sweetie, one bad-ass birthday card, or freak the holy bejesus out of Boston. Your call. It’s a versatile, high-brightness display.
The display can run off an AC adapter or batteries (3 ‘D’ cells), and is designed to run as many green/blue/white/violet LEDs as you care to solder into the holes, all with excellent brightness. The board can accommodate LEDs in several common sizes: 3mm, 5 mm (standard T-1 3/4 size), and 10 mm. A photosensor is provided that can automatically turn off the display in bright daylight or incandescent light.

2. Do I have to put the LEDs on the grid, or can I position them exactly where I want to?

You do not have to place every LED on a regular grid. See the instructions for some tips on how to position the LEDs more arbitrarily.

3. What can I reprogram the display to do?

If you have an appropriate interface and like to program, you can control what the display does, either turning all the LEDs on and off, or controlling the individual rows (but not columns) of the display. Here are some basic ideas to get you started:

Turn on only for a given period of time after it goes dark, or even after a given period of time.

Blink or flash the whole display slowly or occasionally. Use it as a strobe?

Use the photosensor to make the display interactive in other ways– turns on for ten seconds when somebody walks by?

Make an open/closed sign where either the top half or the bottom half of the display is on.

Make a sign with a static logo in one half and blinking text in the other.

Animate vertical waves, fading in and out through the display.

Put different color LEDs in different rows, and alternate how much each of them is driven to make a color changing illumination panel, or a static panel with adjustable color.

LED coffee table?

8-bit style electronic art for your wall or bicycle– it can run on batteries, you know.

LED illumination panel for photography or even an infrared illumination panel.

Use the light sensor, or other sensor with the analog inputs and make a scrolling strip chart that records and displays the history of that variable, plotted by the intensity of the rows of the display.

Attach a sound sensor and make a display or sign that pulses to the beat.

4. What is the “charlieplexing” option/hack?

It’s an alternate configuration (well, a hack, actually) for the board that allows you to control individual LED locations to a limited extent. It requires you to change the hardware around a bit and reprogram the board. It is much dimmer, and doesn’t have enough speed to do anything really complicated. There are also some bugs to work out (A hack with bugs? Never!) that may not make it impossible– or at least very inconvenient– to drive a board that has a lot (note: purposefully left vague) of LEDs on it. So what *can* it do? It can allow very minor animation in limited cases– do you want to blink or wink the eyes on your giant happy face display?

4A. Do you recommend building the multiplexed (standard) or charlieplexed display option?

For almost everyone, the standard option is the way to go. It’s much brighter.

4B. Can I put in 625 LEDs and use this as a full animated display with charlieplexing?

It’s probably possible, but we don’t recommend trying that yet– again, there are some bugs to work out first, and we may need a more severe hack to make it work well.

The clock is working a 24 hour period. The time is displayed in the format "hh: mm: ss" on the alphanumeric display of size 16 x 2 (columns x rows) with driver HD44780. The use of a backlit display gives the impression of great visual at night. Instead, use a full stop or semicolon blink I used options available in the Bascom and created their own simple animation changing every second.With such simple design to evaluate the accuracy of the clock is good. Accuracy was +1 second / 48 hours.Set the clock is simple with 3 buttons.SW1 - is responsible for setting hoursSW2 - for setting minutesSW3 - to go mode of setting time and allows for the approval of the timeout

Video:

To generate signal I used 16 bit counter built into the processor AVR Attiny2313 that the project is incremented with a frequency 8MHz/1024. To overwhelm 16 bit counter within 1 second to load the timer registers the value of((2 ^ 16-1) - (8000000/1024)) = 57822.5 => 57822Timer1 Overflow at the time of service is called interrupt set new values for Timera1, and the modification of global variables responsible for representing the current time.

About microcontroller AVR Attiny2313:ATtiny2313 is 8-bit microcontroller made by Atmel, made in CMOS technology. Attiny2313 builds on RISC architecture. The processor contains 2kB flash memory without removing the stand, 128 bytes of RAM and 128 bytes memory EEPROM. ATtiny2313 has USART interface, 18 universal line input / output and two timers.

Power this project from sunlight with a CirKits solar power circuit board kit.

18 LED dimmable LED lamp

Introduction

This circuit is a dimmable white LED lamp array with 18 LEDs. The lamp brightness is regulated as long as the input voltage is above 10.5V. A low-dropout analog voltage regulator is used for a simple and relatively efficient design. The lamp produces enough light to use as a a reading lamp or a small work lamp.

Specifications

Theory

The 12V DC input voltage is routed through the 1A fuse and the on/off switch. The 1N4001 diode acts as a crowbar device. If reverse polarity is applied, the fuse will blow and the rest of the circuitry will be protected. Power is sent to the LM2941CT voltage regulator IC. The regulator is wired to produce a voltage range from 5.5V (dim) to 8.3V (bright).The 4.7K resistor across the 1K brightness adjustment potentiometer produces a non-linear brightness adjustment to compensate for the eye's logarithmic brightness perception response. The LEDs are organized in six series groups of three with a 24 ohm current limiting resistor on each group. This arrangement limits the maximum current through each LED group to around 20mA.

Use

Connect the DC input terminals to a 12V source, such as a 12V lead acid battery. Be sure to observe the correct polarity. Turn the power switch on and adjust the brightness adjustment for the desired brightness.

New Knight Rider Board, This Third and Best Circuit.Both the Circuit Schematic and the Circuit Board are Below

These circuits will give provide a Good Effect, duplicating the Knight Rider Lights, Plus more.
In the First Circuit
By Changing the Values of the resistors on pins 6 and 7, And/Or the Capacitor
on pin 2 of the 555. you can change Frequency.
I suggest you maintain an Aproximate 50% duty cycle.
This will give an Even Rise and Fall.
But reducing down to 25% can give a reasonable effect also!
In the Second Circuit
In the Second Circuit, the range of Frequency Adjustment should be Quite Sufficient as presented.
But the .47 cap can be changed in Value for other frequencies.
This Circuit is Better than my First Circuit above, as the waveform is more symetrical
and the Drive to the LM3914 is a more stable voltage with more current available.
Changes to the Ratio of the 470K to the 1M Resistor can affect both the Frequency Range
as will as the Waveform Symetry. This could create a Sharp Rise and a Slow Decay,
or Visa Versa. Resulting in Different Visual Effects.
In the Third, Newest Circuit,The Simplest Circuit and Best Yet
The TL082 (Or a TL072 also is OK) Creates an Adjustable Sawtooth Generator.
(It also has a Square wave Output, but it isn't used here.)
The Left and Right LED's are Connected in Series and if this circuit is used on a
12 volt system, and if a person wanted to they could connect 2 LED's for each LED Shown.
Additionally I show the LED's Mounted on the Circuit Board, But they can be wired
OFF Board if So Desired.
1) There is a 1K Pot that adjust the Voltage input to the LM3914.
2) There is a 5K pot that adjust the Output voltage of the Sawtooth Oscillator.
3) There is a 250K Pot to set the Frequency as Desired.
4) Additionally there is a Connection point between Pin 9 of the LM3914.
Joining these together to creates a Bar Display.
5) Substituting an LM3915 or an LM3916 will create a Non-Linear Effect in the Lights.

13 Color LED Rainbow

(C) G. Forrest Cook February 8, 2005

Introduction

Only a few years ago, the choice of LEDs was limited to IR, red, yellow, and green. The LED manufacturers have been busy extending the spectrum, and filling in the gaps. The latest generation of organic LEDs (OLEDs) has added some dazzling new colors to the spectrum. This circuit uses a set of 13 differently colored LEDs to generate a full color spectrum. The photo does not fully represent the colors generated due to camera limitations. The real-world display is very eye-catching. If you want to "trick out" your PC, this circuit is for you. Forget about those boring blue PC light displays

.

Specifications

Operating Voltage: 6-12V DC
Operating Current: 145ma at 12V DC

Theory

The LM2940T-5.0 low dropout voltage regulator converts the 6-12V DC input power to regulated 5 Volts. It was chosen over a standard 7805 regulator so that the circuit could maintain regulation while operating on a 6V battery. The 1N4001 diode protects the circuit from reverse polarity, if a battery or power supply capable of generating over 1 amp is used, a 1 amp fuse should be installed between the supply and the circuit. The 5 Volts is used to drive each of the LEDs through individual current limiting resistors. The resistor values were determined experimentally for equal brightness. Values are given as examples only, different sources of LEDs will require different resistor values. Resistor selection turns out to be the most difficult part of the circuit's construction. A 100 ohm resistor in series with a 1K pot could be used in place of each resistor if individual brightness adjustments are desired. The table below lists the LED colors and wavelengths

.

LED Color

Wavelength

Description

Deep Red

700nm

-

Red

660nm

traditional red

Orange Red

635nm

"high efficiency" red

Orange

623nm

also called red orange

Amber

594nm

-

Yellow

588nm

traditional yellow

Yellow Green

567nm

traditional green

True Green

523mn

-

Cyan

501nm

verde green, blue green

Aqua

495?nm

-

Deep Blue

470nm

ultra blue

Powder Blue

430nm

first generation "powder blue"

Violet

410nm

-

Construction

The circuit was built on a prototype perforated board with printed solder pads. The circuitry is hand-wired on the back side of the board. Care should be taken when soldering to the LEDs, a clip-on heat sink should be used while soldering the leads. Care should be taken to avoid zapping the LEDs on the violet side of the spectrum, they are sensitive to static electricity. The circuit board can be mounted on a piece of white hardboard, the white paint reflects the colors nicely.

Use

Apply power to the circuit and enjoy the colorful glow. Do not stare directly into the array at close range for extended periods, some of the LEDs are extremely bright.

Taking The Circuit Further

The spectrum could be extended on both the IR and UV sides. A brief scan through the Mouser catalog indicates the availability of these IR wavelengths: 940nm 880nm, 875nm, 870nm, 850nm. UV LEDs at 400nm, 395nm and 380nm are also available. There are also many LED colors available with wavelengths between the 13 colors shown, the colors selected were chosen for an evenly spaced color spectrum.

An open-collector LED driver circuit could be connected to the negative LED leads for computer control.

The circuit could be used in conjunction with a photo detector for characterizing optical filter curves. Typically, the photo detector output is sent to a logarithmic converter, the log-ratio of the direct light versus the filtered light characterizes the attenuation at a given wavelength.

Parts

Most of the LEDs were purchased from Digi-Key, Jameco, and Mouser. All of the parts were T1-3/4 size, clear packages were used wherever possible. LEDs from different manufacturers may have different focus characteristics. All of the resistors are 1/4 Watt parts. LED part numbers are not available, the rainbow was assembled from parts that were accumulated over several years. Beware that different LED manufacturers use different names for their colors, the wavelength is the best indicator of the color. The Aqua LED is the most difficult part to find,

I find it somewhat amazing that, to my knowledge, no LED manufacturer has produced a commercial packaging of colored LEDs similar to this project (as of 2006). It would be wonderful if a company would assemble 8 or 10 unique colors into a standard DIP VU meter LED block. It's only a matter of time, I would love to hear about such a part if it ever becomes available.